Latch pivot for latch needle

ABSTRACT

This is a knitting machine latch needle. The latch pivot is formed by displacing portions of the walls of the slot so that the displaced portions extend into the pivot hole of the latch. The displaced portions of the walls are fused together by a high energy heat source emitting sufficient energy to either drill a hole through the displaced portions or melt the displaced portions.

This is a division, of application Ser. No. 265,706 filed June 23, 1972,now U.S. Pat. No. 3,850,011.

This invention relates to knitting machine needles. More particularlythis invention is a new and improved method for making a latch pivot.

Current methods of making latch pivots include using a pair of punchesto displace a portion of the side walls of the blade of the latch needleadjacent the latch slot. The side walls are punched inwardly after thelatch is placed into the latch slot and the latch pivot hole is alignedwith the punches so the displaced portion of the side walls will extendinto the latch pivot hole. The displaced portions may be completelydisplaced or angularly displaced.

Such currently made latch pivots have many advantages over the old screwrivet type. However, in rough service, high speeds and tight loops, thelatch tends to spread the cheeks. This sometimes causes fatiguefailures. In addition, the needle may be slightly spread open, leavingthe latch with less support then it should have. In tightly arrangedknitting elements, such a latch may strike adjacent elements which itshould clear. This leads to wear in areas not intended. Also such extraloose latches do not always behave exactly as do properly supportedlatches. For such reasons, it would be desirable to fuse the twodisplaced portions together. However, to properly fuse the two partstogether is very difficult. This is so, among other things, because thelatch is already in place when the two sides of the latch slot aredisplaced. The latch completely covers the very area you desire to fusetogether.

Our invention is a novel method for fusing together the displacedportions after the latch needle is completely assembled with the latchpivotally mounted on the displaced portions.

The invention as well as its many advantages will be further understoodby reference to the following detailed description and drawings inwhich:

FIG. 1 is a side elevational view showing a portion of a typical latchneedle;

FIG. 2 is an enlarged sectional view showing a regular pressed latchpivot;

FIG. 3 is a view similar to FIG. 2 but showing an angular pressed latchpivot;

FIG. 4 is a top view, partly in section, of a preferred embodiment ofour invention;

FIG. 5 is a top view partly in section showing a second preferredembodiment of our invention;

FIG. 6 is a side elevational view showing the molten metal splashpattern resulting from our invention;

FIG. 7 is a view similar to FIGS. 4 and 5 showing a further modificationof our invention and

FIG. 8 is a schematic of a laser beam which may be utilized inpracticing our new method.

Referring to the drawings, FIG. 1, the latch needle includes a blade 10with a hook 12 on the end of the blade. The latch 14 pivots about pivot16 extending transversely across a slot 18.

FIG. 2 is an enlarged sectional view of a regular pressed pivot. Thelatch pivot is formed by placing the latch 14 with the pivot hole of thelatch in the proper position within the slot 18. The sides 20 and 22 ofthe blade 10 are then punched to form the displaced opposite sideportions 24 and 26. The displaced opposite side portions 24 and 26extend into the pivot hole of the latch 14.

The angular pressed pivot, shown in FIG. 3, is formed by a slightlydifferent shaped punch from the shape of the punch used to form theregular pressed pivot of FIG. 2.

Unfortunately, a space such as space 32 in FIG. 2 or space 34 in FIG. 3usually exists between the two displaced portions. Spaces 32 and 34 areexaggerated in FIG. 2 and FIG. 3, respectively, for clarity. Thesespaces usually run from 0.001 to 0.002 inches. The space is caused bythe spring back of the metal after the displaced portions are formed bythe punch. Previous attempts to weld or fuse the displaced portionstogether have never been completely satisfactory. Electrical dischargemethods often weld segments of the needle not desired, or fail to weldthe non-contacting displaced portions. If the needles are mechanicallyclosed together sufficiently to assure contact of the displacedportions, the latch is often so pinched as to retard its motion. Heatsources other than electricity have been tried but none have provedsufficiently accurate or reliable.

Our new method comprises applying controlled heat from a high energyheat source against at least one of the displaced side wall portions tomelt at least a portion of the side wall portion so that molten metalforms between the two displaced wall portions. The molten metal isallowed to solidify to fuse the two displaced wall portions together.

Since these latch needles are very small, it is necessary that the heatsource be such as to provide the required very well defined and veryaccurate intense heat source. It is now possible to use certain types oflaser beams to provide such required very well defined and very accurateintense heat concentration. One such laser is the Model AO-11 PulsedLaser made by American Optical Corporation of Southbridge,Massachusetts. It is also possible to use a maser beam. Certain types ofelectronic beams may also be used.

As shown in FIG. 4 one way of fusing together the displaced portions 24and 26 is to focus a laser for drilling very fine holes. When the laseris focused to drill fine holes, a small hole 40 extends entirely throughthe center of displaced portion 24. Also a small hole 42 extends throughthe center of displaced portion 26. The holes 40 and 42 may be formed bydrilling from the outside of the side portions 24 and 26 inwardly ordirectly through one side portion 24 or 26. The space between thedisplaced portions 24 and 26 are fused together by the molten metal 44formed from the metal of the displaced portions. The amount of moltenmetal 44 is greatly exaggerated in FIGS. 4, 5, and 7 for clarity. Thefusion results from a splash of molten metal which is melted by thefocused laser beam and boiled out into the space between the parts 24and 26. The molten metal is then allowed to solidify thus fusing theparts 24 and 26 into one unitary pivot for the latch 14. The shape ofthe solidified molten metal 44 is shown in FIG. 6.

Holes similar to holes 40 and 42 in FIG. 4 can be made in the displacedportions 28 and 30 of the angular pressed pivot shown in FIG. 3. It isonly necessary to focus the laser beam in a direction perpendicular tothe outside walls of the angled parts, 28 or 30, or directlyperpendicular to side 20 or side 22.

In FIG. 5 instead of penetrating entirely through both displacedportions 24 and 26 the drill hole 40 extends entirely through theportion 24 but then only slightly into portion 26. The fused metalportion 44 pattern is the same as in FIG. 6.

In the embodiment shown in FIG. 7, the laser was focused to melt themetal rather than to drill a hole through the metal. This is done bymoving further from the focal point, preferably toward the laser itself.The laser beam is hot enough to melt the metal but lacks sufficientenergy to boil the metal. The result is that the inwardly displacedportion 24 which was hit from the outside by the laser beam has aportion of its metal melted and when the metal portion 44 solidifies isfused to the portion 26 leaving a concave shape 48 on the outside ofportion 24. If desired, the laser beam could be applied not only to thedisplaced portion 24 but also against the outside of the displacedportion 26. In such case, a concave surface would also be formed on theoutside of the displaced portion 26.

FIG. 8 is a schematic illustration of a laser or maser beam. Theparallel rays of light 50 are focused by a lens 52 with the mostconcentrated energy being at the focal point 54. To drill holes such asholes 40 and 42 in FIG. 4, the displaced portions are placed at thefocal point 54 of the laser beam. However, if it is desired not tocompletely boil the metal but only to melt the metal, the displacedportions are placed along the line 56--56.

We claim:
 1. In a method of forming a latch pivot for the latch of alatch needle, having portions of the opposite walls of the slot in theneedle displaced into a pivot hole of the latch, with a space betweenthe displaced portions and with spaces separating the latch from each ofthe opposite walls of the slot, the improvement comprising the steps of:applying controlled heat from a high energy heat source against at leastone of said displaced wall portions to at least melt a portion of saiddisplaced wall portion so that molten metal is formed in the spacebetween the two displaced wall portions; the extent of the molten metalbeing controlled to substantially fill said space without contacting thelatch and allowing the molten metal to solidify to fuse the displacedwall portions together without changing the spaces separating the latchfrom each of the opposite walls of the slot.
 2. The method of forming alatch pivot in accordance with claim 1 wherein the molten metal isformed by applying heat of sufficient thermal energy to the outside ofsaid displaced wall portion to make a small hole entirely through saiddisplaced wall portion to form a splash of molten metal between the twodisplaced wall portions.
 3. The method of claim 2 wherein a small holeis formed through both of the displaced wall portions.
 4. The method ofclaim 1 wherein the molten metal is formed by applying against saiddisplaced wall portion a high energy heat beam of sufficient energy tomelt at least a portion of said displaced wall portion.